How to use SPE on MPC8541

Gérard Guével gguevel at
Thu Sep 29 23:23:51 EST 2005

> Hmm... This is very strange, because Dhrystone is exactly the
> benchmark this was tested on.  How did you determine that the SPE
> functions are called?

I prefix the strcpy and strcmp functions with a "v" in dhry21a.c and
dhry21b.c. Then I statically compile the c files with the freescale
assembly source S files and not with the library libcfsl_e500.a.

If I don't add the S files the ld fails else it succeeds.
I retreive the symbols vstr... in the binary dhrystone with readelf.
So I presume that it is the right code that is called.

> I'm not sure why you aren't seeing a performance gain, but I assure
> you that, if SPE instructions weren't working, Dhrystone would
> crash.

I confirm that if I try to run this binary without SPE in Linux kernel
I get an exception.

> The only other possibility I can think of is that the SPE
> versions of the functions aren't being called.

I don't understand what you say.
Perhaps have you a pre-compiled dhrystone for Linux 2.6
I can try and compare on my board


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